DESCRIPTION: This is the midlife follow-up phase of the earliest, largest, and most comprehensive pre-DSM-III U.S. study of boys with the constellation of behavior problems that includes what is currently called Attention-Deficit/Hyperactivity Disorder (ADHD). This phase will involve 364 subjects in four groups: (1) 164 probands who were medicated as children with a central nervous system stimulant such as methylphenidate for an average of 3 years (the MED group), (2) 50 probands who were never medicated (UNMED), (3) 75 unreferred and never medicated full brothers of these 214 probands (BRO), and (4) 75 normal boys drawn from middle school classrooms of the probands during an adolescent follow-up (CLASS). The probands have been followed by the current research team since their referral for diagnostic evaluation and treatment to the University of Iowa outpatient child psychiatry clinic between 1967 and 1978. Their data were used to derive and validate Loney and colleagues' two-factor model for (1) assessing inattention-overactivity (10) and aggression-defiance (AG) in boys with behavior problems, (2) placing such boys into symptomatically homogeneous diagnostic subgroups (10, AG, IO+AG, and neither), and (3) predicting their adolescent and young adult outcomes. All subjects will be comprehensively evaluated between ages 35 and 45 in psychiatric, psychological, cognitive, neuropsychological, and psychosocial domains to describe their midlife functioning and to answer questions about selected adult psychiatric outcomes: adult/residual ADHD, personality disorders (e.g., antisocial, paranoid, schizotypal, and avoidant), adult bipolar spectrum disorders (mania, hypomania, and cyclothymia), depression, and alcohol and drug use, abuse, and dependence. Diagnostic information will also be obtained from 433 parents. As children, probands were assigned to medication conditions essentially randomly. Therefore, the investigators will be able to compare the midlife outcomes of (1) MED and UNMED groups to determine the long-term impact of childhood stimulant medication and (2) UNMED ADHD and CLASS groups to determine the impact of ADHD, thus separating the effects of the disorder from the effects of its most common and controversial treatment. Analyses within the MED group will identify which aspects of medication (initial response, maintenance dosage, treatment duration) predict midlife outcomes. The investigators will also examine the external validity of the two-factor JO and AG dimensions and the DSM-IV ADHD inattentive, hyperactive-impulsive, and combined subtypes. Additional information will be available to determine the associations of the probands' childhood and adult disorders with the childhood symptoms of their sons and daughters. This study will provide valuable information about the diagnosis, midlife prognosis, and generational transmission of ADHD and related disorders and about the long-term effects of stimulant medication.